Dielectrically extensible boom structure

ABSTRACT

An extensible boom structure of a dielectric type in which a plurality of telescopic members some of which are made of a dielectric material are slidably mounted together to provide a telescopic boom structure with motive means for extending and retracting sections of the same being mounted internal of the boom structure and made in part of a metal and part of a dielectric material. The parts are connected respectively to portions of the boom structure of the same material to maintain dielectric isolation in the boom length. Provision is also made in the improved extensible boom structure of mounting additional extensions.

United States Patent Kennedy 1 1 Oct. 24, 1972 [5 DIELECTRICALLY EXTENSIBLE 3,353,686 11/1967 Cowan ..212/55 BOOM STRUCTURE 3,243,052 3/1966 Grove ..212/55 2,918,224 12/1959 Harnberger ..92/118 X [72] Invent Ray Kennedy 2,918,039 12/1959 Boje etal ..92/118 x [73] Assignee: Tel-E-Lect, Inc., Minneapolis, Minn. 2,404,904 7/1946 Collins"; ..52/309 X [22] Flled: 1971 Primary Examiner-Martin P. Schwadron [21] Ap l No 169,137 Assistant Examiner-R. H. Lazarus Attorney-Schroeder, Siegfried & Ryan Related US. Application Data [63] Continuation of Ser. No. 882,661, Dec. 5, [57] ABSTRACT 1969, abandoned. An extensible boom structure of a dielectric type in which a plurality of telescopic members some of [52] US. Cl. ..92/119, 92/118, 212/55 which are made of a dielectric material are slidably [51] Int. Cl ..F0lb 15/04 mounted together to provide a telescopic boorn struc- [58] Field of Search ..92/55, 117, 118, 119, 57; ture with motive means for extending and retracting 212 55 55 X 52 113 309 sections of the same being mounted internal of the boom structure and made in part of a metal and part [56] References Cited of a dielectric material. The parts are connected respectively to portions of the boom structure of the UNITED STATES PATENTS same material to maintain dielectric isolation in the boom length. Provision is also made in the improved 3,516,553 6/1970 Reske ..52/118 X 3,415,169 12/1968 Naddell ..92/117 x Structure mmmmg addmnal R26,442 8/1968 Dunbar ..212/55 XR 3,398,645 8/ 1968 Nansel ..52/1 15 13 Claims, 4 Drawing Figures PATENTEDUCT 24 1972 SHEET 1 [IF 2 PATENTEDucI 24 I972 SHEET 2 UF 2 INVENTOR. Ray L. Kennedy MWWW- ATTORNEYS DIELECTRICALLY EXTENSIBLE BOOM STRUCTURE This is a continuation of US. Pat. application Ser. No. 882,661, filed Dec. 5, 1969, now abandoned.

My invention relates to an extensible boom structure and more particularly to an improved extensible boom structure of the dielectric type.

Mobile aerial platforms, aerial platform trucks and equivalent structure are well known in the use and have employed a dielectric section in the past for the purpose of safeguarding equipment and personnel from electrical shock during work in and around electric current carrying equipment. Normally, such equipment includes a personnel carrying basket and it is necessary for safety to incorporate dielectric isolation of the platform or basket when working under the lines of current-carrying transmission lines or the like. Prior structures have incorporated motive means with the purpose of elevating portions of the boom relative to one another with a motive means being positioned external at the boom structures thus facilitating incorporation of dielectric material in portions of the boom. Normally, the base or root section will be made of a steel and the fiberglass or dielectric sections are pivoted thereon. These units have a fixed length and are exceedingly massive structures with restricted modes of movement and articulation. Where telescopic elements are used in the boom, prior structures have involved complex cabling systems with isolating portions to insure dielectric isolation of the boom extremity. Such structures prohibit the use of additional equipment on the boom and limit adjustability of the same.

In the present invention, an improved extensible boom structure of a dielectric type is provided which utilizes an internally mounted actuator for slidably extending and retracting sections of the boom. The entire structure may be articulated and/or the end of the boom may include an articulated arm and the base of the boom is normally made of metal for strength purposes. The telescopic sections are made of a dielectric material, such as fiberglass, and the motive means is positioned within the boom element and connected respectively to portions of the same for linearly slidably retracting and extending the same, the linear fluid actuator comprising a cylinder and actuating shaft. Within the present invention the linear actuator is made in part of a dielectric material and in part of a metal material with the dielectric portion being connected in common to the dielectric telescopic inner boom members with the purpose of maintaining the dielectric isolation or electrical isolation of the boom elements. Within the scope of the present invention, a variety of connections for the actuator is provided which will also permit the mounting of additional structures on the extension such as manually extended auxiliary sections for special purposes.

Therefore, it is the principal object of this invention to provide an improved extensible boom structure of a dielectric type.

Another object of this invention is to provide an improved boom structure with internal actuators and dielectric isolation of the same.

A further object of this invention is to provide an extensible boom structure in which the actuators are formed part of a metal material and part of a fiberglass material and connected to boom sections to maintain dielectric isolation of the boom sections.

Another object of this invention is to provide an improved extensible boom structure with a mounting for an additional extensible boom element where linear actuators are employed within a boom structure.

These and other objects of this invention will become apparent from a reading of the attached description together with the drawings wherein:

FIG. 1 is a sectional view of a portion of the boom structure showing the extensible portion in a retracted position;

FIG. 2 is a sectional view similar to FIG. 1 showing the extensible portion in an extended position;

FIG. 3 is an alternate embodiment of the boom structure shown as a sectional view with the extensible portions in a retracted position; and

FIG. 4 is a sectional view similar to FIG. 3 showing the extensible portions in an extended position.

My improved dielectrically extensible boom structure as shown in the drawings is a fragmentary showing of a plurality of telescopic boom elements with a complete detail of the boom, its supporting structure, actuators and controls being omitted for simplicity since they form no part of the present invention. Any type of supporting vehicle and boom mounting may be employed and similarly any type of platform or tool may be included on the extremity of the boom structure for working purposes. The invention is particularly applicable and restricted to boom structures which incorporate telescopic parts and in which the extremities of the boom structure are made of a non-conducting or dielectric material.

Thus, in the drawings, the root extremity of the boom structure or the main boom element is shown broken away and identified generally as 10. This structure is preferably made of metal, such as steel, and will be oriented in azimuth and elevation through any suitable structure. This main boom structure indicated at 10, may in fact be a second or slidably mounted boom connected with the base boom structure and for the purpose of maintaining isolation of the boom extremity with the metal parts, at least one extensible boom element or structure 20 will be slidably mounted within the extremity of the boom element 10 which extensible boom element 20 will be made of a dielectric material, such as fiberglass. The length of the boom element may vary and it may carry either a personnel carrying platform or basket or suitable working tools such as a winch or auger at the end of the same. The boom elements 10 and 20 are moved relative to one another, that is, retracted and extended by means of an actuator positioned within the boom structure, such as will be shown in the drawings. Thus, as will be seen in FIG. 1, an elongated linear actuator, which may be of the pneumatic or hydraulic type, is included within the confines of the boom elements 10 and 20 with its cylinder 30 and actuating shaft 40 being connected respectively to the boom elements.

In order to maintain-the dielectric integrity or spacing between the boom parts in the extended position, the actuator which is connected thereto must also be dielectrically separated Thus, it will be seen in FIGS. 1 and 2, the cylinder portion 30 of this linear actuator will be made of metal material, such as steel, and is pivotally mounted at the closed extremity of the same through a pin 35 extending through a journal member 32 and pivot bearing members 34 positioned on the inner wall of the boom element these latter parts would also be made of metal. Although not shown, it will be understood that the bearing members 34 and the pin 35 would be so mounted in the boom structure as to permit removal of the same whenever it is desirable to remove the actuator. The actuator includes a piston member 38 which will be normally made of metal material that includes suitable sealing surfaces with the piston member being carried by the operating shaft 40 which is made of a dielectric material, such as fiberglass. The operating shaft 40 extends through a suitable joumaling aperture in the opposite end wall of the cylinder, as at 42. The exposed extremity of the operating shaft mounts a journal member 44 which is pivotally mounted through a pin 47 extending therethrough and joined in suitable bearing structures 46 on either side of the same affixed to the inner side of the extensible element 20. Preferably, these parts are all made of a dielectric material, such as fiberglass or plastic.

In the retracted position of the boom structure as shown in FIG. 1, extensible element will be positioned suchthat it substantially encircles the cylinder 30 of the actuator. Suitable clearance is provided therebetween to allow fluid connections 49 to connect with either end of the actuator to provide for bidirectional operation of the same. Similarly, suitable conventional guide structures such as rollers (not shown) will be attached to the boom structure 10 to engage and guide the extensible element 20 as it moves and to maintain the spacing therebetween. In this retracted position, the actuating shaft 40 and its connection with the extensible element 20 will be located within the confines of the extremity of the boom structure 10. The pivotal connections at both extremities of the linear actuator provides for smooth operation of the same compensate for any looseness or disalignment of the telescopic parts forming the boom structure as they extend and retract. The length of the linear actuator will control the length of the extension and retraction of the extensible element with respect to the boom 10, and as will be seen in FIG. 2, the movement of the piston 38 within the cylinder 30 upon application of fluid pressure behind the piston will permit extension of the extensible element 20 to its maximum extent wherein the piston will abut the shaft end of the cylinder. That portion of the extensible element extending beyond the metallic end of the boom structure or element 10 will be of a dielectric material insuring positive dielectric isolation between the free end of the extensible element and any equipment or platform connected thereto (not shown) and the metallic portion of the boom structure. This will provide the desired dielectric isolation while maintaining a varied degree of extensibility of the boom structure.

An alternate embodiment of this extensible boom structure is shown in FIGS. 3 and 4. In this embodiment the main boom structure 10 is again made of steel or similar metal and slidably mounts in the telescopic manner a pair of inner extensible elements, indicated generally at 50 and 60. In this embodiment, the linear actuator which extends and retracts the extensible portions 50 and 60 of the boom structure relative to the boom 10 is reversed in position from the before-mentioned embodiment in FIGS. 1 and 2. Thus, the shaft 55 of the actuator is connected to the boom element 10 while the cylinder 65 is connected to the extensible elements 50 and 60. The operating shaft 55 carriw the piston 56 which parts are made of metal with the shaft being journaled through a journal member 58 in bearings 59 by a pin 57 positioned in and on the boom 10. The cylinder 65 is made of a fiberglass material that is formed integral with or connected to the extensible boom element 50 with a suitable dielectric connecting portion 66 which connects the open end or shaft end of the cylinder with the inner surface of the extensible element 50. The extensible element is spaced therefrom providing a recessed area or surface in which the extensible portion 60 is carried and is adapted to move. The extensible element 50 is guided on the boom element 10 through suitable and conventional guide members or roller (not shown) in a conventional manner which maintains the spacing therebetween. Similarly, it will be understood that with the cylinder movement the fluid connections to the extremities of the cylinder would have to be flexible and extendable to follow cylinder movement. Suitable inlet passages indicated generally at 70 may be provided through the operating shaft 55 which remains stationary to either side of the piston within the cylinder to provide the fluid passages to either end of the cylinder for reversible actuator movement in a conventional manner. In this embodiment, the cylinder itself is fixed to the extensible portion 50 of the boom structure rather than being pivoted thereon and the cylinder and extensible portion may be formed as a single unit with a spacing therebetween for the purpose of slidably mounting the additional extensible element 60 which will be extended and retracted manually or by other means. Further, this form of the boom structure will require a pneumatic as distinguished from liquid power medium for reversing the actuator. to maintain complete dielectric integrity of the extended portion of the boom structure. The free end of the extensible element 60 may mount a pulley to be used for directing a cable from the winch (not shown) normally mounted on the metallic or root portion of the boom or may carry other tools to be used as desired. Although not shown, it will be understood that the extensible portion 60 may be positioned relative to the extensible portion 50 manually and pinned in the desired location to increase the overall length and maintain the dielectric extent of the same.

In my improved extensible boom structure, provision is made for extending portions of the same relative to a metallic base portion with the portions extended being made of a dielectric material and that portion of the actuator which extends beyond the metallic portion being made of a dielectric material to insure complete dielectric integrity and insolation of the portion of the boom extended beyond the metallic root or main boom portion. Such extensions may carry working tools, personnel carrying baskets and the like to insure electric insulation between the boom extremity and the metallic portions thereof.

What is claimed is:

1. An extensible boom structure comprising, 'a hollow boom element and a hollow tubular extensible element telescopically mounted therein for extension and retraction relative thereto, a two part linear actuator for extending and retracting said extensible element with respect to the boom element, means mounting one part of the actuator to the interior of the boom element, means mounting the other part of the actuator to the interior of the extensible element and such that the parts of the actuator are positioned within the confines of the boom element for the retracted position of the actuator and the extensible element, said extensible boom element being made of a dielectric material and at least that portion of the part of the actuator which extends out of the confines of the boom element with extension of the extensible element and the actuator being made of the same material.

2. The extensible boom structure of claim 1 in which said parts of said actuator have a range of linear movement co-extensive with a range of extension and retraction of the extensible element relative to the boom element.

3. The extensible boom structure of claim 1 in which the boom element is made of a metal material.

4. The extensible boom structure of claim 2 in which the two part linear actuator is a'linear fluid actuator having a cylinder body with a piston therein and an actuating shaft attached thereto for movement thereby and extending out of the cylinder body.

5. The extensible boom structure of claim 3 in which the linear actuator is reversible.

6. The extensible boom structure of claim 4 in which the piston is always made of a metal material and wherein at least one of the cylinder body or actuating shaft are selectively made of a dielectric material.

7. The extensible boom structure of claim 1 in which the mounting means for mounting said one part of said actuator to the interior of the boom element includes a pivot means for pivoting the actuator relative to the boom element.

8. The extensible boom structure of claim 7 in which the cylinder is pivotally mounted on the interior of the boom element.

9. The extensible boom element of claim 7 in which the shaft is pivotally mounted on the interior of the boom element.

10. The extensible boom structure of claim 7 and in which the mounting means for mounting the other part of the actuator to the interior of the extensible element includes a pivot means for pivoting said other part of 6 the actuator relative to the extensible element.

11. The extensible boom structure of claim 10 in which the parts of the linear actuator mounted respectively on the boom element and the extensible structure are the cylinder pivotally connected to the boom element and the actuating shaft pivotally connected to the extensible element.

12. An extensible boom structure comprising, a hollow boom element and a hollow tubular extensible element telescopically mounted therein for extension and retraction relative thereto, a two part linear actuator for extending and retracting said extensible element with respect to the boom element, means mounting one .part of the actuator to the interior of the boom element, means mounting the other part of the actuator to the interior of the extensible element and such that the parts of the actuator are positioned within the confines of the boom element for the retracted position of the actuator and the extensible element, said extensible boom element being made of a dielectric material and at least that portion of the part of the actuator which extends out of the confines of the boom element with extension of the extensible element and the actuator being made of a dielectric material, and means carried by the extensible element and adapted to be moved with the extensible element upon extension and retraction of the actuator, said means being dielectrically isolated from the boom element, said two part linear actuator having a linear fluid actuator with a cylinder body of dielectric material mounted in the inner surface of the extensible element and an actuating shaft of metal material mounted through a pivotal connection to the inner surface of the boom element with the mounting of the extensible member on the cylinder body being positioned on the end of the cylinder body adjacent to the actuator shaft to define an annular recess between the cylinder body and the extensible element.

13. The extensible boom structure of claim 12 in which the means carried by the extensible element is a second boom extension telescopically mounted therein and extending into the annular recess between the cylindrical body of the actuator and the extensible element in the retracted position and being made of a dielectric material. 

1. An extensible boom structure comprising, a hollow boom element and a hollow tubular extensible element telescopically mounted therein for extension and retraction relative thereto, a two part linear actuator for extending and retracting said extensible element with respect to the boom element, means mounting one part of the actuator to the interior of the boom element, means mounting the other part of the actuator to the interior of the extensible element and such that the parts of the actuator are positioned within the confines of the boom element for the retracted position of the actuator and the extensible element, said extensible boom element being made of a dielectric material and at least that portion of the part of the actuator which extends out of the confines of the boom element with extension of the extensible element and the actuator being made of the same material.
 2. The extensible boom structure of claim 1 in which said parts of said actuator have a range of linear movement co-extensive with a range of extension and retraction of the extensible element relative to the boom element.
 3. The extensible boom structure of claim 1 in which the boom element is made of a metal material.
 4. The extensible boom structure of claim 2 in which The two part linear actuator is a linear fluid actuator having a cylinder body with a piston therein and an actuating shaft attached thereto for movement thereby and extending out of the cylinder body.
 5. The extensible boom structure of claim 3 in which the linear actuator is reversible.
 6. The extensible boom structure of claim 4 in which the piston is always made of a metal material and wherein at least one of the cylinder body or actuating shaft are selectively made of a dielectric material.
 7. The extensible boom structure of claim 1 in which the mounting means for mounting said one part of said actuator to the interior of the boom element includes a pivot means for pivoting the actuator relative to the boom element.
 8. The extensible boom structure of claim 7 in which the cylinder is pivotally mounted on the interior of the boom element.
 9. The extensible boom element of claim 7 in which the shaft is pivotally mounted on the interior of the boom element.
 10. The extensible boom structure of claim 7 and in which the mounting means for mounting the other part of the actuator to the interior of the extensible element includes a pivot means for pivoting said other part of the actuator relative to the extensible element.
 11. The extensible boom structure of claim 10 in which the parts of the linear actuator mounted respectively on the boom element and the extensible structure are the cylinder pivotally connected to the boom element and the actuating shaft pivotally connected to the extensible element.
 12. An extensible boom structure comprising, a hollow boom element and a hollow tubular extensible element telescopically mounted therein for extension and retraction relative thereto, a two part linear actuator for extending and retracting said extensible element with respect to the boom element, means mounting one part of the actuator to the interior of the boom element, means mounting the other part of the actuator to the interior of the extensible element and such that the parts of the actuator are positioned within the confines of the boom element for the retracted position of the actuator and the extensible element, said extensible boom element being made of a dielectric material and at least that portion of the part of the actuator which extends out of the confines of the boom element with extension of the extensible element and the actuator being made of a dielectric material, and means carried by the extensible element and adapted to be moved with the extensible element upon extension and retraction of the actuator, said means being dielectrically isolated from the boom element, said two part linear actuator having a linear fluid actuator with a cylinder body of dielectric material mounted in the inner surface of the extensible element and an actuating shaft of metal material mounted through a pivotal connection to the inner surface of the boom element with the mounting of the extensible member on the cylinder body being positioned on the end of the cylinder body adjacent to the actuator shaft to define an annular recess between the cylinder body and the extensible element.
 13. The extensible boom structure of claim 12 in which the means carried by the extensible element is a second boom extension telescopically mounted therein and extending into the annular recess between the cylindrical body of the actuator and the extensible element in the retracted position and being made of a dielectric material. 